The present invention relates to treatment accessories that are inserted into a forceps channel of an endoscope and are used for treating an affected part on human tissue or the like.
One such treatment accessory is a cytology brush used for collecting cells inside a human body.
The process of brushing cytology is well known. In this process, a brush instrument is used to brush mucous or the like in order to collect cells or the like on bristles of the brush instrument. According to a conventional endoscope structure, when withdrawing a brush instrument through a forceps channel of the endoscope, cells that have adhered on the brush may be scraped or knocked off of the bristles either at the inlet of the forceps channel or within the forceps channel itself.
In order to avoid the problem above, a brush instrument provided with a cover tube may be used. In such a brush instrument, a brush portion having bristles is arranged to be movable in relation to the cover tube so that the brush portion can be projected from or retracted inside the cover tube. When cell are to be collected, the brush portion is projected from the cover tube, brushed against the human tissue to collect the cells, and then retracted inside the cover tube. After the brush portion is retracted inside the cover tube, the brush instrument (i.e., the brush portion and the cover tube) is retracted through the forceps channel.
However, when the mucous is brushed and mixture of the cells and the mucous adheres on the bristles of the brush, some cells are sandwiched among the bristles, while other cells remain near the outer tips of the bristles, such that, even with the cover tube, the cells near the tips of the bristles may be scraped off by the end of the cover tube when the brush is retracted inside the cover tube. Therefore, even using the brush instrument having the cover tube, it is difficult to obtain a relatively great amount of cells at a time.
In such a brush instrument, this problem could be avoided by arranging the brush instrument such that a diameter of the brush portion, including the bristles, is less than the diameter of the cover tube. However, if a smaller brush diameter is used, the amount of cells collected in one brushing operation is relatively small, and it may be difficult to obtain a sufficient amount of cells in one brushing operation.
If another instrument such as a grasping forceps instrument is used as the treatment accessory, a similar problem arises. That is, when forceps that are grasping a mucous or tissue are retracted in the forceps channel, a part of the mucous or tissue may be knocked off by the end of the forceps channel. Even if the cover tube is employed, a similar problem as discussed above occurs.